This invention relates generally to turbine engines and, more particularly, to a system and methods for improved cooling in turbine engines.
Gas turbine engines tipically include a core engine having, in serial flow relationship, a multistage axial flow low pressure compressor and a multistage axial flow high pressure compressor which supplies high pressure airflow to a combustor. The compressors include stages of stationary components referred to as stators and stages of rotational components, which add work and compress the airflow entering the core engine system, referred to as rotors.
A portion of the high pressure compressed airflow supplied to the combustor is mixed with fuel, ignited, and utilized to generate hot propulsive combustion gases which flow further downstream to one of the multistage flow paths. Particularly, the combustion gases flow through one or more turbine stages which extract energy from the hot propulsive combustion gases to power the rotors in the compressors and provide other useful work. For example, a high pressure turbine may be rotated by the hot propulsive combustion gases and may be connected to the high pressure compressor by a shaft so that the high pressure turbine drives the rotors in the high pressure compressor.
A typical bypass turbine engine adds a low pressure turbine, aft of the high pressure turbine, to drive the low pressure compressor and a front fan. The front fan is located forward of, and drives, the airflow into the low pressure compressor. The airflow that does not enter the core engine through the low pressure compressor is directed through a fan bypass duct by a flow splitter. The bypass airflow from the fan exists the fan bypass duct to provide most of the engine thrust. The rest of the engine thrust comes from the core engine airflow after it leaves the turbine stages and is accelerated out of the exhaust nozzle.
Turbine engines are constructed to operate at high temperatures to maximize engine thrust. Cooling of engine components, such as components of the high pressure turbine, is necessary due to thermal stress limitations of materials used in construction of such components. Typically, cooler airflow is extracted from an outlet of the compressors and the cooler airflow is used to cool, for example, turbine airfoils.
For example, a portion of the low pressure compressed airflow may be extracted from the low pressure compressor for turbine section cooling, airframe pressurization, anti-icing, and other uses. Increasing the pressure of the airflow in the compressors increases the relative temperature of the airflow as well and makes it desirable to extract the airflow from the compressors after the minimum number of stages. Unfortunately, the relatively low pressure and hot temperature of the airflow limits the effective use of the compressed airflow to cool such engine components.
Accordingly, it would be desirable to provide cooler airflow to high temperature turbine engine components. Additionally, it would be desirable to increase the pressure of the cooler airflow to cool more components and reduce the amount of cooling air utilized.